1. Technical Field
The present invention relates generally to surfacing pads and, in particular, to pads used in conjunction with lens lapping tools for creating optical and ophthalmic lenses. More specifically, the present invention relates to an attachment system for attaching optical and ophthalmic lens surfacing pads to lens lapping tools.
2. Discussion
Optical and ophthalmic lenses are generally made by generating a lens blank to the approximate curvature on a lens generator and then surfacing (by way of grinding, lapping, fining, or other similar procedures) the lens with an abrasive slurry and an oscillating lapping tool. Surfacing is generally defined as the process of creating an optical surface in an ophthalmic lens. Lapping tools are usually cast iron, aluminum, or plastic tools having various lapping surfaces, each of a curvature corresponding to a desired lens curvature. Thus, an optical manufacturer requires a set of lapping tools in order to manufacture lenses of various prescriptions.
Modernly, surfacing pads which conform exactly to the lapping tool curvature are generally used on the surface of each lapping tool. Typically, lenses are also subjected to a polishing procedure. Polishing is generally defined as the process of imparting clarity to an optical lens.
These surfacing pads, sometimes commonly referred to as lapping or polishing pads, usually wear relatively quickly and are generally replaced after a single lens is ground. However, surfacing pads provide a relatively inexpensive surface which will wear instead of the relatively more expensive lapping tool.
Recently, improved surfacing pads have been developed which contain an abrasive material (typically referred to as lapping abrasive), such as, but not limited to, sandpaper or diamond particles, either on the surface of the pad or impregnated into it. Typically, the abrasive content or efficiency of the surfacing pad decreases as grinding progresses to lapping. There is generally very little or even no abrasive content in the surfacing pads employed during the fining and polishing stages.
As an illustration of the differences between surfacing and polishing procedures, glass surfacing involves fining a lens on a cast iron lapping tool, with or without a metal lapping tool pad, with a loose abrasive slurry. Glass polishing, on the other hand, involves polishing a lens on a lapping tool covered with a polishing pad of wool or PELLON.TM. using a polishing slurry poured over the lapping tool.
One surfacing procedure using such pads involves adhesively attaching a first sandpaper fining pad to a lapping tool and grinding a lens under running water to the proper curve (i.e., the grinding or fining stage). Generally, a second sandpaper fining pad of relatively smaller grit than the first sandpaper surfacing pad is placed over and adhered to the first sandpaper surfacing pad wherein the lens is subjected to a second surfacing step under running water (i.e., the lapping stage). Next, both surfacing pads are removed from the lapping tool, wherein a flocked (e.g., velveteen) polishing pad is adhered to the tool and the lens is polished to a clear finish under a polishing slurry (i.e., the polishing stage). The aforementioned surfacing procedure can be used for both glass and plastic lenses.
Although conventional surfacing pads have aided in the production of optical and ophthalmic lenses, they have certain disadvantages and drawbacks. For example, an operator must frequently attach and remove the surfacing pads which are adhesively secured either to the surface of the lapping tool or to a pad on the surface of the tool and can be difficult to peel off the lapping tool. Frequent removal and reattachment of these surfacing pads may result in the eventual failure of the adhesive to properly hold the surfacing pad in place during the various surfacing operations. Even if the surfacing pads remain in place, the edges of the surfacing pads have the tendency to eventually lift up from the surface of the lapping tool or become damaged by handling, thus affecting the performance of the surfacing pad and leading to surface irregularities and blemishes on the resulting lens. Furthermore, the surfacing pads can be difficult to attach to the tools without the formation of wrinkles, which adversely effect the performance of the surfacing pad. Coolant water flowing over the surfacing pads serves to further increase the difficulties encountered in attaching and removing the surfacing pads.
Therefore, there exists a need for an improved lens surfacing pad and method of attachment therefor which reduces or eliminates these disadvantages and drawbacks. The present invention provides such an improved lens surfacing pad and method of attachment therefor.
Additional objects, advantages, and features of the present invention will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings.